The present invention relates to a rechargeable light curing apparatus, especially for curing dental materials such as tooth filling materials, comprising a hand-operated device having a battery pack with at least one accumulator and an electric connection for recharging the battery pack, wherein with a switch operated by the operator a lamp for generating a defined light emission state is switched on and the emitted light is received by light conducting elements arranged within the vicinity of the lamp.
Such irradiation devices for curing of materials that are curable by radiation are, for example, known from European patent application 166 364. In general, they contain a light source, a light conducting element and a coupling means between the light conducting element and the light source. In this context and in the following, light is to be understood as electromagnetic radiation of a suitable frequency whereby it is understood that, in general, all suitable types of radiation can be employed.
In the known radiation device the light source is a fluorescent tube that is supplied with electricity with a cable, a power supply transformer, a battery, or an accumulator. When having an accumulator, the hand-operated device may be provided with a plug connection for recharging.
However, it has been demonstrated that light curable materials cure insufficiently when the light curing is not performed in the prescribed manner. Therefore, in such devices the accumulator, if possible, must always be completely charged in order to provide the full light intensity at all times. However, this results, as is well known in the art, in a degradation of the capacity of the accumulator due to the memory effect. In an advanced stage this is reversible only to a certain degree. A reversion of the memory effect is furthermore complicated and success is not guaranteed when the memory effect is advanced.
Due to these difficulties and the critical operation parameters, a fast exchange of the used accumulators is therefore required for accumulator-operated dental treatment devices which is disadvantageous for various reasons.
A simple light curing device is also known in which accumulators are also provided. In this device a mechanical counter registers the number of times the device has been switched on. The switched-on state is, for example, preset to 20 seconds, and after a predetermined number of switched-on states it is presumed that the accumulators are discharged to such a degree that a further time period for a polymerization step is no longer available. After this point in time, a complete recharging of the accumulator is performed. Only thereafter is the device again operable.
This light curing device has great disadvantages. On the one hand, the recharging time of the accumulators is too great. On the other hand, the surveillance of the light intensity of the device by mechanically counting the number of switched-on states and the blocking of the device after a certain number of switching steps is very unsatisfactory. The light curing device only counts the switching steps and thus a defined time without taking into consideration the actual capacity of the accumulator. A further disadvantage is that the device must be completely recharged every time in order for the device to provide for an effective control. Furthermore, each time a certain operating period must be observed, and the memory effect is not taken into consideration.
These facts represent great disadvantages because the dentist must rely, without being able to check, on the light intensity of the lamp; however, the required intensity may no longer be available so that the dental filling material will not be cured or will be incompletely cured, resulting in defects. When using such a device, liability claims cannot be prevented.
Other accumulator-operated dental treatment devices are known from U.S. Pat. No. 3,109,238 and U.S. Pat. No. 3,509,629. The accumulators in these devices are recharged by a commercial recharging unit. In the alternative, it is provided to use single-use batteries. Single-use batteries allow for a quick reuse of the dental treatment device; however, they are considered environmentally unsafe, and their use is relatively expensive. Furthermore, the exchange of the batteries requires the opening of the hand-operated device. This, however, is undesirable in a medical environment.
It is therefore an object of the present invention to provide a rechargeable lightcuring device of the aforementioned kind that provides for an improved usability, without the accumulator voltage reaching values critical for the operation of the light curing device.